Help me! for the love of god! help!

Here's the problem:

I recently installed a Viper GC Extreme and first flashed Cobra 2.1,

which worked very well, but than I got stupid and tried flashing GCOS

1.5...and that worked...but now I don't know how to flash back to

Cobra....I can't even get any freaking games working with

GCOS....please, please, please help me....within fifteen minutes of

finally getting everything working, i've messed it up!